I've got a ZoomContentControl with its CenterPoint two-way bound to a property in my ViewModel:
<navigation:ZoomContentControl CenterPoint="{Binding CenterPoint, Mode=TwoWay} IsVirtualSpaceEnabled="True"">
When dragging the view, this CenterPoint property gets updated - even if the view is not actually moving (due to it having reached the 'edge' of the virtual space, for instance). The values seem to indicate dragging "past" when the view actually stops moving; if you then release the mouse & begin dragging again, the numbers "jump" back to where they should've remained previously.
Here's a video to show this behavior: http://screencast.com/t/K80LC8M8JVJh
As you can see, once I get to the top left of the virtual space, the view stops moving (the visible centerpoint stops changing), yet the values keep increasing (the printouts are coming from the ViewModel's property setter). I then let go & begin dragging again - and the values jump back to where they were.
The behavior is the same with & without VirtualSpace enabled.